The Security and Exchange Commission’s Office of Investor Education and Advocacy offers these online security tips:
Pick a “strong” password, keep it secure, and change it regularly.
Select a strong password for your online brokerage account. A strong password is one that isn’t easy to guess and generally uses eight or more characters that include symbols, numbers, and both capital and lowercase letters. A strong password is not based on common words, phrases, or personal information such as a name or birthday. Keep your password in a safe place and out of plain sight. Never share your password on the Internet, by e-mail, or over the phone. In addition, you should change your password regularly.